diff --git a/fs/aio.c b/fs/aio.c
index e4598d6..f8b8e45 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -108,8 +108,8 @@ static int aio_setup_ring(struct kioctx *ctx)
 	unsigned long size;
 	int nr_pages;
 
-	/* Compensate for the ring buffer's head/tail overlap entry */
-	nr_events += 2;	/* 1 is required, 2 for good luck */
+	/* round nr_event to next power of 2 */
+	nr_events = roundup_pow_of_two(nr_events);
 
 	size = sizeof(struct aio_ring);
 	size += sizeof(struct io_event) * nr_events;
@@ -118,8 +118,6 @@ static int aio_setup_ring(struct kioctx *ctx)
 	if (nr_pages < 0)
 		return -EINVAL;
 
-	nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring)) / sizeof(struct io_event);
-
 	info->nr = 0;
 	info->ring_pages = info->internal_pages;
 	if (nr_pages > AIO_RING_PAGES) {
@@ -177,14 +175,16 @@ static int aio_setup_ring(struct kioctx *ctx)
 #define AIO_EVENTS_FIRST_PAGE	((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
 #define AIO_EVENTS_OFFSET	(AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
 
-#define aio_ring_event(info, nr, km) ({					\
-	unsigned pos = (nr) + AIO_EVENTS_OFFSET;			\
-	struct io_event *__event;					\
-	__event = kmap_atomic(						\
-			(info)->ring_pages[pos / AIO_EVENTS_PER_PAGE], km); \
-	__event += pos % AIO_EVENTS_PER_PAGE;				\
-	__event;							\
-})
+static struct io_event *aio_ring_event(struct aio_ring_info *info,
+					unsigned nr, enum km_type km)
+{
+	unsigned pos = (nr & (info->nr - 1)) + AIO_EVENTS_OFFSET;
+	struct io_event *event;
+
+	event = kmap_atomic(info->ring_pages[pos / AIO_EVENTS_PER_PAGE], km);
+	event += pos % AIO_EVENTS_PER_PAGE;
+	return event;
+}
 
 #define put_aio_ring_event(event, km) do {	\
 	struct io_event *__event = (event);	\
@@ -220,7 +220,6 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 
 	atomic_set(&ctx->users, 1);
 	spin_lock_init(&ctx->ctx_lock);
-	spin_lock_init(&ctx->ring_info.ring_lock);
 	init_waitqueue_head(&ctx->wait);
 
 	INIT_LIST_HEAD(&ctx->active_reqs);
@@ -927,7 +926,7 @@ int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
 	struct aio_ring	*ring;
 	struct io_event	*event;
 	unsigned long	flags;
-	unsigned long	tail;
+	unsigned	tail;
 	int		ret;
 
 	/*
@@ -969,8 +968,6 @@ int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
 
 	tail = info->tail;
 	event = aio_ring_event(info, tail, KM_IRQ0);
-	if (++tail >= info->nr)
-		tail = 0;
 
 	event->obj = (u64)(unsigned long)iocb->ki_obj.user;
 	event->data = iocb->ki_user_data;
@@ -986,13 +983,14 @@ int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
 	 */
 	smp_wmb();	/* make event visible before updating tail */
 
+	tail++;
 	info->tail = tail;
 	ring->tail = tail;
 
 	put_aio_ring_event(event, KM_IRQ0);
 	kunmap_atomic(ring, KM_IRQ1);
 
-	pr_debug("added to ring %p at [%lu]\n", iocb, tail);
+	pr_debug("added to ring %p at [%u]\n", iocb, tail);
 put_rq:
 	/* everything turned out well, dispose of the aiocb. */
 	ret = __aio_put_req(ctx, iocb);
@@ -1007,39 +1005,35 @@ put_rq:
 /* aio_read_evt
  *	Pull an event off of the ioctx's event ring.  Returns the number of 
  *	events fetched (0 or 1 ;-)
- *	FIXME: make this use cmpxchg.
  *	TODO: make the ringbuffer user mmap()able (requires FIXME).
  */
 static int aio_read_evt(struct kioctx *ioctx, struct io_event *ent)
 {
 	struct aio_ring_info *info = &ioctx->ring_info;
 	struct aio_ring *ring;
-	unsigned long head;
-	int ret = 0;
+	struct io_event *evp;
+	unsigned head;
+	int ret;
 
 	ring = kmap_atomic(info->ring_pages[0], KM_USER0);
 	dprintk("in aio_read_evt h%lu t%lu m%lu\n",
 		 (unsigned long)ring->head, (unsigned long)ring->tail,
 		 (unsigned long)ring->nr);
 
-	if (ring->head == ring->tail)
-		goto out;
-
-	spin_lock(&info->ring_lock);
-
-	head = ring->head % info->nr;
-	if (head != ring->tail) {
-		struct io_event *evp = aio_ring_event(info, head, KM_USER1);
+	do {
+		head = ring->head;
+		if (head == ring->tail) {
+			ret = 0;
+			break;
+		}
+		evp = aio_ring_event(info, head, KM_USER1);
 		*ent = *evp;
-		head = (head + 1) % info->nr;
 		smp_mb(); /* finish reading the event before updatng the head */
-		ring->head = head;
 		ret = 1;
 		put_aio_ring_event(evp, KM_USER1);
-	}
-	spin_unlock(&info->ring_lock);
+	} while (head != atomic_cmpxchg((atomic_t *) &ring->head,
+					head, head + 1));
 
-out:
 	kunmap_atomic(ring, KM_USER0);
 	dprintk("leaving aio_read_evt: %d  h%lu t%lu\n", ret,
 		 (unsigned long)ring->head, (unsigned long)ring->tail);
diff --git a/include/linux/aio.h b/include/linux/aio.h
index a30ef13..0cd66a3 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -156,7 +156,7 @@ struct aio_ring {
 	struct io_event		io_events[0];
 }; /* 128 bytes + ring size */
 
-#define aio_ring_avail(info, ring)	(((ring)->head + (info)->nr - 1 - (ring)->tail) % (info)->nr)
+#define aio_ring_avail(info, ring) ((info)->nr + (ring)->head - (ring)->tail)
 
 #define AIO_RING_PAGES	8
 struct aio_ring_info {
@@ -164,7 +164,6 @@ struct aio_ring_info {
 	unsigned long		mmap_size;
 
 	struct page		**ring_pages;
-	spinlock_t		ring_lock;
 	long			nr_pages;
 
 	unsigned		nr, tail;